ci : create pre-release with change log and nightly link in make-release (#27302)

* ci : create pre-release with change log and nightly link in make-release

After pushing the tag, create a pre-release using
ggml-org/action-create-release. The release description is generated by
scripts/make-release-desc.sh: the change log between the current and
previous version (one line per commit), a link to the corresponding
nightly build when it exists, and a note that semantic versioning is
still work in progress.

Assisted-by: pi:llama.cpp/Qwen3.8-27B

* cmake : bump version to 0.1.2

Assisted-by: pi:llama.cpp/Qwen3.8-27B

* ci : find the nightly tag by commit in make-release-desc.sh

The nightly release is guaranteed by the release checks to point at HEAD,
so instead of reconstructing its name (commit count, branch, hash) just
pick the b* tag pointing at HEAD. This also drops the RELEASE_BRANCH env
var from the workflow.

Assisted-by: pi:llama.cpp/Qwen3.8-27B

* ci : resolve the release commit from the version tag in make-release-desc.sh

The change log and nightly lookup now use the commit the version tag
points at (HEAD when the tag does not exist), instead of always HEAD.
This makes the script usable locally for older versions, e.g.
./scripts/make-release-desc.sh v0.1.1. The tag is resolved to a SHA
first, since --points-at does not peel annotated tags.

Assisted-by: pi:llama.cpp/Qwen3.8-27B

* ci : normalize the version argument in make-release-desc.sh

Accept the version with or without the leading v (0.1.1 == v0.1.1) and
reject anything else, instead of silently treating a bare version as a
non-existent tag name.

Assisted-by: pi:llama.cpp/Qwen3.8-27B

* cont : clean-up

.github/workflows/make-release.yml

@@ -49,6 +49,33 @@ jobs:
           git push origin "${VERSION}"
           echo "Created and pushed tag ${VERSION}"
 
+      - name: Generate release description
+        id: desc
+        run: bash scripts/make-release-desc.sh "${{ steps.checks.outputs.version }}"
+        env:
+          GITHUB_REPOSITORY: ${{ github.repository }}
+
+      - name: Create release
+        if: ${{ github.event.inputs.dry_run == 'false' }}
+        uses: ggml-org/action-create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ github.token }}
+        with:
+          tag_name: ${{ steps.checks.outputs.version }}
+          # TODO: remove the prerelease flag once the semantic versioning workflow is ready
+          # ref: https://github.com/ggml-org/ggml/discussions/1579
+          prerelease: true
+          body: |
+            > [!NOTE]
+            > Semantic versioning is still work in progress.
+            > More info can be found in https://github.com/ggml-org/ggml/discussions/1579
+
+            ${{ steps.desc.outputs.nightly }}
+
+            ## ${{ steps.desc.outputs.changelog_title }}
+
+            ${{ steps.desc.outputs.changelog }}
+
       - name: Dry run summary
         if: ${{ github.event.inputs.dry_run == 'true' }}
         run: |